Apparatus for spray-bonding tissue

ABSTRACT

Multi-ply tissue product is bonded by an adhesive spray whose position is controlled so that the web path distance between the spray application and the location where the webs are forced together permits sprayed adhesive to partially but not completely set during travel over that web path distance at operating web speeds. Typically, the web path distance between the nozzle and the location is more than 140 inches. The webs are positioned one in back of the other and each is unwound onto its own carrier roll, with the spray positioned between the carrier rolls.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. applicationSer. No. 09/649,775, filed Aug. 29, 2000 (issued as U.S. , on ,) whichin turn was a divisional application of U.S. application Ser. No.08/628,386, filed on Apr. 5, 1996 (issued as U.S. Pat. No. 6,136,422, onOct. 24, 2000). This application claims priority to, and incorporates byreference the entirety of, both of the above U.S. patent applications.

TECHNICAL FIELD

[0002] This invention is in the general field of multi-ply tissueproducts as well as methods and apparatus for bonding tissue plies tomake such products.

BACKGROUND

[0003] Various tissue products are made by laminating multiple layers oftissue. These layers or plies must be bonded to prevent them fromdelaminating or floating apart when they are converted into the finalproduct or when they are used by the consumer.

[0004] Ply bonding of the individual tissue sheets into multi-ply layersis usually achieved by embossing them on converting equipment withoutapplying adhesive. In this process, two or more tissue webs aresimultaneously unwound and fed through a nip formed between male andfemale embossing rolls to emboss or crimp the webs and thereby bond themtogether. Often in making such products as napkins, the webs areembossed only around the perimeter of areas that will be cut into theindividual napkins.

[0005] In a different process, tissue plies may be adhered using achemical adhesive rather than by embossing. For example, Bjork U.S. Pat.No. 5,466,318 discloses a process for laminating webs using awater-based adhesive.

[0006] Controlling ply bonding is important and difficult. Inadequate,excessive or inconsistent ply bonding can jam complex, high-speedmachinery, generate high waste, and provide unacceptable product. Thestrength of bonding by embossing (without adhesive) may vary depending,among other things, on water content or dryness of tissue webs, and onambient air humidity. While bonding by embossing sometimes can beimproved by increasing the pressure on the embossing rolls, suchpressure can wear out the embossing rolls more quickly, particularly thefemale roll, which is usually a softer roll made of composite materialonto which a pattern is impressed by the opposing, male, engraved metalroll. In addition, the journals and bearings of both embossing rolls canalso wear out prematurely if subjected to increased pressure over aprolonged period.

[0007] The use of adhesives can avoid some of the problems of embossing,but adhesives also cause problems, such as “through bonding” or“blocking”, in which adjacent laminates bond to one another, and,prevent unwinding of the laminate product from its roll. Non-uniformityof bonding also causes problems, such as wrinkling of the tissue and badprinting.

[0008] As noted, the bonding process may be part of the overall processfor making the final multi-ply product. For example, multi-ply tissueproducts, particularly napkins, may be printed, e.g., by a letterpressor a flexographic process. In a typical letterpress printing process, amulti-ply web is first embossed, and then the central unembossed area ofindividual napkins is printed. In an alternative flexographic printingprocess, unbonded webs may be first run through a flexographic printingtower and then crimped with an embossing nip.

[0009] While the invention has broader application, we referspecifically to certain markets, particularly high quality napkins suchas the party goods, food service, and other specialty napkin markets.These markets may require cloth-like character and feel, high wetstrength, and the ability to be decorated with high quality printing.Increasingly, these markets have expressed preference for quality andcomplexity provided by flexographic printing.

[0010] It can be difficult to achieve cloth-like character and feelwhile also achieving satisfactory bonding of two or more plies of tissueto make one sheet of napkin tissue that will not come apart either whenused by the consumer or when subjected to flexographic printing. Thenapkin must not de-ply, it must stay in one piece like a cloth napkinwould. However, the use of adhesives and other additives to develop theresistance to ply separation tends to make the product stiff and destroythe cloth-like feel.

[0011] Another product requirement in this field is the need of strengthwhile wet, which can be critically important to high quality papernapkins. Non-wet strength napkins may pull apart when subjected tomoisture, such as spilled liquid or a wet glass, rendering thenunsatisfactory for the high quality markets. Chemicals normally employedto impart wet strength (e.g., urea, phenol-formaldehyde) can reduce plybond-strength, which is already problematic, and can make the napkinstiffer.

[0012] With regard to decorated or printed napkins, certain napkinmachines (e.g., those made by Servotec and Hoberna), which useflexographic printing have stringent ply requirements. As noted, theseflexographic machines print the napkin first and emboss it afterwards,in contrast with letterpress napkin machines, which first emboss theedges of the napkin so that the plies of tissue are crimped together,after which the napkin is printed. In the flexographic process, it iscritical that the plies be held together without embossing while thenapkin is being printed. Floating plies as the tissue enters theprinting stage result in jams and high waste together with machinedowntime. In addition, the application of the ink causes the top layerof the tissue to expand if the plies are not well bonded, resulting inwrinkling, badly printed napkins, and extremely high costs from waste.

[0013] These problems are sometimes addressed by the use of much heaviernapkin tissue (as has been done in Europe where some of the flexographicmachines were introduced). Heavier tissue is more expensive.

SUMMARY

[0014] We have discovered spray bonding processes and apparatus thatprovide substantially improved efficiency and process control of tissuebonding. The resulting adhesively bonded intermediate product isimproved, particularly for use in flexographic printing applications.The final product may be a paper napkin, a paper towel, a medicaldisposable towel, a table cover or other similar tissue product. Thecloth-like feel achieved by the invention is suitable for a wide rangeof markets, including not only markets where softness is important butalso markets where a certain amount of product stiffness is required,such as the markets in which napkins are forced into plastic wrapscontaining cutlery (napkins made and packaged by “Austin-Gordon” or“Gordon”-type machines)

[0015] In particular, the invention provides a well-bonded napkinproduct that can be used in converting apparatus, particularlyflexographic printing apparatus. This ply-bonded tissue is constructedof lighter weight material that is less costly than the previously usedtissue (particularly in Europe), yet the tissue exhibits printabilityand a cloth-like feel. Cloth-like character and feel, high wet strength,printability and low cost are achieved in a reliably ply-bonded productwithout the need to emboss before printing. The result is markedlyenhanced ply bonding of the tissue layers and efficient and high qualityprinting, without detracting from the cloth-like character and feel thatthe use of adhesives can cause.

[0016] One aspect of the invention generally features a multi-plyadhesively bonded tissue roll with an extremely limited amount of wasteat the core, which results from the absence of bonding or poorlycontrolled bonding during start-up of the bonding process. The rollcomprises a bonded region that extends to within at least ¾ inch of thecore. (This ¾ inch measurement is made from the outer diameter of thecore, which is typically about 4 inches to the point in the product atwhich adhesive bonding begins.) Adhesive contact between the plies issubstantially continuous over the bonded region of the roll (i.e., atradiuses greater than ¾″), and the strength throughout the bonded regionof the roll is high, substantially without through bonding in thatregion. While bond strengths of at least 100 mg/cm are achieved, in oneparticular embodiment, the bond strength is at least 400 mg/cm.

[0017] In another aspect of the invention described below, we have foundthat careful process control permits lower adhesive loading and the useof a pressurized nip to force the webs together without unacceptableadhesive build-up on the nip rolls, particularly for two-ply tissueproduct. Strong two-ply adhesion can be achieved with lower adhesiveloading, thus avoiding problems caused by inconsistent adhesive loadingwhile at the same time enabling better control over winding tension(because the nip controls tension transmitted upstream). Thus, thisaspect of the invention features methods of producing an adhesivelybonded two-ply tissue product by: spraying an adhesive mixture upwardlyonto one of the moving webs from at least one nozzle array positioned ina spray location below one of the webs; compressing the webs together asthey run through a nip formed by two nip rolls positioned at acompression point downstream of the spray location; and winding thebonded two-ply tissue product onto a roll under tension using a winderwhich pulls the two-ply product, exerting tension on it. In this aspectof the invention, it is practical to use a pressurized nip to force theadhesively bonded webs together. The distance between the spray locationand the nip is selected to permit sprayed adhesive to partially but notcompletely set during travel over that distance at operating web speeds.The webs may be forced together with nip rollers that have enoughpressure to substantially confine winder tension to the nip-to-winderportion of the web path, as opposed to transmitting winder tensionupstream to the parent reels (i.e. the reels on which the tissue stockhas been supplied to the bonder), thereby providing improved controlover winder tension. Because the spray location is carefully controlled,it is possible to use such a nip without unacceptable adhesive build-upon the nip rolls.

[0018] In the above process, the adhesive is considered to be partiallybut not completely set when it has what is known in the field as “greentack”. At that stage, the adhesive is damp to the touch, but it does nottransfer to another surface, so the adhesive will contact bond, but itwill not migrate so far through the tissue web that it causes throughbonding as the bonded webs are wound into a roll.

[0019] Typically, each tissue web is unwound over its own carrier roll,and spray nozzle(s) are positioned between the carrier rolls,particularly adjacent to and downstream of the rear carrier roll. Forexample, the web travel distance between the nozzles and the nip is morethan 140 (and even more than 200 but less than 500) inches.

[0020] In a third aspect, the invention features methods of producingtissue product with more than 2 (usually 3 or 4) plies. The method usesat least two spray nozzle arrays, a rear array to spray the bottom of anupper web and a forward array to spray the bottom of an intermediateweb. The multiple webs are tensioned by a winder around a compressionroll (usually but not necessarily a nip roll as described above) tocompress the webs. The web travel distance between the two nozzle arraysand the nip roll is controlled so that adhesive is partially but notcompletely set when it reaches the roll. Both nozzle arrays arepositioned as discussed above. Typically the forward nozzle array willbe more than 140 inches (preferably more than 200 inches) from thecompression roll.

[0021] Preferably, webs are run at a speed of well over 1500 feet/min(more preferably 2,300 feet/min or higher), and the dwell time foradhesive applied to the web is between 0.3 and 1.3 seconds. Dwell timeis the period from application of adhesive to the web until the adhesivetreated web reaches the nip.

[0022] Alternatively, to make three- or more ply product, the number ofsprayer locations may be two less than the number of plies being bound.For example, four moving webs are positioned vertically to form an upperweb, a upper-middle web, a lower-middle web, and a bottom webrespectively, and only two arrays of adhesive spray nozzles are used: afirst array positioned in the rear location to spray upwardly onto thebottom surface of the upper-middle web; and a second array positioned ina third location to spray upwardly onto the bottom of the lower-middleweb. Similarly, the method may be used to make three-ply tissue bypositioning three moving webs as an upper web, a middle web, and a lowerweb, respectively, and using only one adhesive nozzle array, which ispositioned in the rear location to spray upwardly onto the middle web.

[0023] A significant advantage of the method is that it can be used inseries with high-speed tissue-forming equipment, i.e., reels of tissuewebs are provided by forming them on equipment including a dryer, andwinding up the resulting webs, which then are bonded at a rate whichexceeds the rate at which the webs are produced. When we say that thewebs are bonded at a rate which exceeds the rate at which the webs areproduced, we take into account down time at the beginning of a run forloading reels of freshly made unbonded tissue and time at the end of arun to unload bonded multi-ply tissue. We also take into account similardown time for the tissue production process. Finally, we take intoaccount that at least two and sometimes three or four tissue webs mustbe made to produce a single multi-ply bonded web so that, as a roughapproximation and if all other things were equal, a two-ply bondingprocess could run at ½ the speed of the tissue manufacturing processwithout becoming a bottleneck. In general, the web speed exceeds 1500feet/min (preferably over 2000 feet/min) during a significant portion ofthe bonding process.

[0024] Tissue making relies on management of the creping process, inwhich dried tissue is scraped from a heated drying cylinder to which ithas been adhered. Creping is improved generally when the drying cylinderis hot and the tissue is relatively dry at the point of creping. Theabove described bonding process is advantageous in that it can bondrelatively dry webs, without adding or retaining moisture at thetissue-forming stage to accommodate the needs of the bonding process.

[0025] Control over the spray process may include controlling theadhesive mixture flow with respect to web travel speed, for example, tomaintain a substantially constant (+or −20%) overall rate of addition ofdry adhesive per unit area of web at different speeds (preferably theaddition rate is between 5 and 25 (most preferably between 5 and 20)pounds/million square feet of multi-ply web). The method may alsoinclude controlling the air pressure used to spray the mixture atdifferent web travel speeds.

[0026] Typically, the method includes at least two phases, a runningphase and a substantially slower transition phase (e.g., starting up orslowing down the winder). The amount of liquid adhesive delivered perminute is substantially proportional (±20%) to the web speed during boththe running phase and the transitional phase. The atomizing airflowpressure or flow rate may also be controlled responsive to changes inweb travel rate between the running and the transition phase.

[0027] Multiple nozzles may be positioned on supports in a showerhousing which includes a drain for over-spray. The shower housingincludes a damper that is movable from a first damper orientation thatprevents nozzle spray from reaching the moving web to a second damperorientation in which spray reaches moving web. During the start-upphase, the damper is positioned in the first orientation so that web isnot bonded. The shower housing may be raised from a an inactive positionduring idle periods when the web is slowed or stopped to a second activeposition. Adhesive may be purged from the nozzles in a cycle thatincludes introducing flush water and/or airflow into the shower nozzle.

[0028] Preferred adhesives are aqueous mixtures, e.g., of carboxymethylcellulose; polyvinyl alcohol; or starch. The spraying process controldescribed above enables the use of higher (for example at least 13%)solids in the liquid adhesive, which in turn results in shorter dryingtimes.

[0029] After the adhesive is applied, the webs may be forced together bya pair of rolls (e.g. calender rolls) that are in contact as the twowebs pass through. For example, these rolls may be biased together toform a pressure nip. The bonded tissue plies are then wound up on awinder downstream of the nip, and tension on the winder is substantiallymaintained downstream of the nip and is not substantially communicatedupstream of the nip.

II. Apparatus

[0030] The above method is practiced using apparatus that includes:

[0031] A. a rear reel stand and a rear carrier roll above the rearstand, forming the beginning of an upper web path;

[0032] B. a forward reel stand and a forward carrier roll above theforward stand, forming the beginning of a lower web path, the upper webpath converging with the lower web path at the forward carrier roll;

[0033] C. an adhesive applicator system for applying adhesive to thebottom of tissue moving in the upper web path, the adhesive applicatorsystem comprising:

[0034] i. an array of spray nozzles positioned at a spray location belowand generally transverse to the upper tissue path, and oriented to spraygenerally upward, toward the bottom surface of the upper tissue, thefirst location being between the rear and the forward carrier rolls;

[0035] ii. an air pressure source connected to provide air to the spraynozzles

[0036] iii. an adhesive source connected to provide a flow of adhesiveto the spray nozzles, and

[0037] D. a pair of nip rolls positioned downstream from the spray headarray and the forward carrier roll, the nip rolls being in both theupper and lower tissue paths, the nip rolls forming a nip forcompressing the upper and the lower tissue together

[0038] E. a winder downstream of the nip for winding up bonded tissueproduct, the winder being designed to have a running speed within apredetermined range, the nip being spaced apart from the spray locationat least 230 inches, to permit sprayed adhesive to partially but notcompletely set during travel over that distance at speeds in thepredetermined range.

[0039] The location of the array of spray heads is controlled asdescribed above. For example, the nip is spaced apart from the first(rear) location by at least 200 inches to permit sprayed adhesive topartially but not completely set during travel over that distance.Specifically, the array is located between the rear and the forwardcarrier rolls.

[0040] The apparatus may also include: A. an adhesive pump providing aflow of adhesive to the spray heads; B. an air pump providing airpressure to the spray heads; C. a sensor for sensing the speed of travelof at least one of the tissue webs, which provides a web speed signal toa signal processor; and D. an adhesive flow control system forcontrolling the flow of adhesive to the spray heads; the adhesive flowcontrol system includes a flow rate monitor, a signal processor whichreceives a signal from the monitor and provides signals to an adhesiveflow motor, responsive to the web speed signal, so that the adhesivedelivery rate is varied in response to web travel rate.

[0041] When more than two tissue webs are being bound, the apparatusincludes at least one intermediate reel stand and intermediate carrierroll, forming the beginning of an intermediate web path, theintermediate carrier roll being positioned between the rear and theforward carrier rolls. The apparatus may also include additional arraysof spray heads positioned at a second (forward) location below andgenerally transverse to the intermediate web path, and oriented to spraygenerally upward, toward the bottom surface of the intermediate tissue.

[0042] The apparatus can operate fast enough to process the output ofthe web-forming equipment substantially without backlog or slowing ofthat equipment.

[0043] A signal processor includes circuitry to control the amount ofadhesive flow supplied to the nozzles substantially proportional to theweb travel speed, so as to provide a substantially constant overallratio of dry adhesive per unit area of web at different web speeds. Thecontroller also includes circuitry to establish the other methodcontrols described above, such as the controls on adhesive flow, airflowdamper position, and shower housing position. The controller alsocontrols a purge cycle in which flush water and/or airflow is directedinto the nozzle.

[0044] As noted, the above process and apparatus use tissue that is verydry without need for further modification. The process avoids the needto emboss as a bonding process. The process permits effective use ofhigh speed tissue forming machinery. The process improves utilizationand reduces waste, particularly waste from discarding the beginning andend of rolls due to improper adhesive loading at transition speeds.

[0045] The details of one or more embodiments of the invention are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the invention will be apparent fromthe description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

[0046]FIG. 1 is a diagram showing apparatus for spray bonding two movingtissue webs.

[0047]FIG. 2 is a chart of a operating sequences during a process forspray bonding moving tissue webs.

[0048]FIGS. 3A through 3C are top, front and side views, respectively,of a shower housing.

[0049]FIG. 4 is a diagram of the valves and supply conduits for thehousing of FIGS. 3A-3C.

[0050]FIG. 5 is a sectional view of a nozzle.

[0051]FIG. 6 is a diagram of controls for the apparatus of FIG. 1.

[0052]FIG. 7 shows an alternative embodiment for producing four-plytissue.

[0053] Like reference symbols in the various drawings indicate likeelements.

DETAILED DESCRIPTION

[0054] In FIG. 1, individual tissue webs 10 and 20 are spray bonded onply bonder 40 to form a two-ply tissue product 30. Bonder 40 includestwo reel stands 42 and 44 suitable to receive webs as they are producedby tissue forming apparatus (not shown).

[0055] Webs 10 and 20 are unwound from the reel stands and threaded overcarrier rolls 46 and 48 to roll 49 and from there to calender rolls 50and 52 and winder 54.

[0056] A shower assembly 60 is positioned between carrier rolls 46 and48, beneath, and across the width of (i.e. transverse to the movementof), web 10. Shower assembly 60 (shown in greater detail in FIGS. 3A-3C)includes a row of nozzles (shown in FIG. 4) positioned in a rectangularhousing 64, which extends across the width of the web (about 112 inches)and the housing section (FIG. 3C) is about 9×11 inches. Housing 64(shown for clarity in FIGS. 3A-3C without nozzles) includes severalfeatures described in greater detail below. Axle 66 extends across thewidth of the housing, and it controls rotation of a baffle plate (or“flapper”) 68. A trailing lip 70 extends from the rear (trailing) edgeof housing 64. Side ports 72 are provided for air adhesive conduits(shown in FIG. 4) which supply nozzles 62.

[0057]FIG. 4 shows an array of 12 nozzles 62 spaced about 8.75 inchescenter-to-center. Generally, the number of nozzles is selected toprovide 200% coverage—i.e., any given point on the web generallyreceives output from two nozzles. As described in greater detail below,each nozzle is connected to a liquid adhesive supply 63, and atomizingair supply 65 and a control air supply 67.

[0058] A representative nozzle 62 is shown in FIG. 5. The nozzlecomprises a control chamber 74 which drives a shut-off and clean-out pin76 to shut off or open orifice 78. Adhesive is supplied from one sideport 80, and air is supplied from an atomizing air port 82 on the otherside of the nozzle. The pressure in chamber 74 overcomes the springbias, driving pin 76 rearwardly and opening orifice 78. Generally, thenozzle produces a fine flat fan spray with a fairly wide spray angle(thus reducing the number of nozzles needed). The wider the spray angle,the fewer nozzles that are required, thus reducing costs and generallystabilizing and maximizing adhesive flow in any single nozzle.

[0059]FIG. 6 is a diagrammatic representation of the systems that supplyand control the equipment described above.

[0060] Shower assembly 60 and supply conduit 63 are connected toadhesive reservoir 102 and supply pump 103 via supply conduit 104, whichincludes filter 105 and valve 120. Pump 103 is a positive displacementpump, driven by a variable speed motor to control adhesive flow. Amagnetic flow meter 107 monitors flow in conduit 104. Valves 120 and 121as a pair can be set to direct adhesive flow to conduit 63 (valve 120open and 121 shut) or to return loop 123 which returns adhesive tosupply 102 when valve 121 is open and 120 is shut.

[0061] The shower assembly is connected to atomizing air supply conduit65 (introduced through both sides of housing 60) from air supply 106.Atomizing airflow is controlled by supply valve 109.

[0062] Nozzle control air is provided via conduit 67, and is controlledby pneumatic valve 134, which is supplied by air supply 106.

[0063] Flapper control arm 69 is connected to pneumatic controller 71,which is supplied from via air supply conduit 106. Flush water supply 91is connected to atomizing air supply conduit 65 via control valve 115and check valve 117. Shower housing assembly lift mechanism 108 iscontrolled by pneumatic valve 131 which is pressurized by air supply 106via conduit 133.

[0064] Quick purge valve 140 opens the atomizing air conduit 65 to purgeany liquid in it at the end of the purge cycle described below.

[0065] A computer (signal processor) 100 is separately connected toadhesive supply pump 103 and to air supply valve 109. Computer 100 isalso connected to control the speed of pump 103 responsive to signals itreceives from: a) flow meter 107; b) operator input of the adhesive flowset point; and c) winder speed. Computer 100 is also connected to othercomponents as described above and shown in the figures.

[0066] A system of compressed air supply 106 supports the number ofoperations described above, e.g., it provides pressure and volume tooperate the spray nozzles and various system components described below.The compressed air capacity required will vary depending on the needs ofa particular system. Generally, a source on the order of 40 CFM at 80psi is adequate.

[0067] Computer 100 reads the winder speed (WS), the adhesive flow (AF)and any control modes supplied by operator input 113. From these values,computer 100 calculates the required adhesive flow (AF), so thatAF=K×WS×SP, where WS is the winder speed; SP is an operator supplied setpoint for the adhesive loading—i.e., dry weight of adhesive per area ofweb. The set point for making a two-ply product typically will be on theorder of 5-25 (more preferably 5-20) pounds of dry adhesive per millionsquare feet of web. When three-ply tissue is made with two showers, eachshower is set in the above range. Where a single shower is used to bondthree plies, the adhesive spray must penetrate the middle layer to bondboth the upper and lower layer. In that event, the set point for thatshower is higher (e.g. in the range of 30-35 pounds/million squarefeet). “K” is a proportionality constant that takes into account thewidth of the winder, the density of adhesive mixture (gallons of mixtureper unit of dry adhesive weight) and that reconciles and scales unitsused.

[0068] Computer 100 also is programmed with routines to

[0069] 1. start, stop and control the speed of the adhesive feed pumps;

[0070] 2. start, stop and regulate atomizing air;

[0071] 3. turn control air on and off;

[0072] 4. open and close the flapper;

[0073] 5. raise and lower the shower box;

[0074] 6. toggle adhesive diverting valves;

[0075] 7. flush the shower by,

[0076] i. starting and stopping flush water,

[0077] ii. opening and closing the quick purge valve,

[0078] iii. starting and stopping the atomizing air;

[0079] The operation of the above-described equipment will be betterunderstood with reference to the following operating sequencesdiagrammed in FIG. 2. Overall operation can be divided into a start-upcycle, a normal running mode, and a shutdown cycle. The operator mayselect manual or automatic operation. At rest (col. 1), the winder isoff, a run interlock is open, the adhesive flow is off, the atomizingair is off, the shower housing is in the lower, inactive position, theflapper is closed, the control air is off, valves in the adhesive flowloop are set to recycle adhesive to the supply (i.e., valve 120 isclosed and valve 121 is open), flush water is closed, and purge air isclosed.

[0080] In automatic operation, the computer begins start up with athreading mode (col. 2) by turning the winder on to a slow, threadingspeed, and turning on the pump to begin adhesive flow (with valve 121remaining open and valve 120 remaining closed). The computer then entersa mode in which the web is running (col. 3) by closing the runinterlock, turning on the atomizing air valve 107, and moving the showerhousing and the flapper into operating positions. Once the web runningstatus is achieved, there are two two-second speed-up checks (cols. 4and 5) as the winder speed is increased. Control air is turned onbetween these two checks.

[0081] Immediately after the second speed check, diverter valve 121 isclosed and supply valve 120 is opened to start adhesive flow to thenozzles. The apparatus is then in its normal running mode (col. 6).

[0082] Shut-down includes several phases, and it may be initiatedmanually or automatically as the winder slows and a low speed threshold(e.g. <100 feet/min) is reached.

[0083] In shut down, atomizing air is ramped down with the winder, andthen both are turned off. The run interlock is opened, and adhesive flowis diverted by closing valve 120 and opening valve 121. The showerhousing is lowered and the flapper is closed. Nozzle control airpressure is also shut off.

[0084] A nozzle wash cycle is achieved by introducing flush water intothe atomizing air conduit 65. A nozzle air purge cycle (col. 9) isachieved by turning off flush water, and starting atomizing air flowingthrough the nozzles. Atomizing airflow is increased for the final purge(col. 10) by opening quick purge valve 140 at the far end of the nozzlehousing. When the atomizing air and quick purge valve 140 are turnedoff, the system is at rest (col. 12).

[0085] A flush mode as described above can be instituted manuallywhenever the shower is in auto mode and the winder is not running. Thewater valve will stay open for as long as 15 minutes (compared to the 15seconds in the auto mode).

[0086] A manual mode permits each of the control functions to beoperated manually and independently.

[0087] Bond strength of the product may be tested according to astandardized protocol. For example, small strips of bonded product(typically about 2.5 inches wide) are subjected to known force todetermine the amount of force required to separate the tissue layers. Ingeneral, for flexographic product applications, the bond strength shouldexceed 100 mg/cm. Preferably the median value of the bond strengthshould be over 400 mg/cm. If necessary, the measured force forseparating a given strip may be doubled using two strips, and obtaininga value for separating both strips.

[0088] Because the product is bonded with a carefully controlledadhesive spray, the adhesive is substantially continuous and uniform,even when analyzed at a detailed level. For example, when a starch orPVA adhesive applied by the above spray is evaluated using a standardiodine visualizing procedure (e.g., spraying a 0.01N I₂ solution on thetissue from a standard pump sprayer), color development indicative ofadhesive shows very little non-uniformity, and what non-uniformityexists is generally random, at least over areas greater than 1 mm². Incontrast, adhesive applied by a textured roll will show a regularuniform matrix of starch dots over areas up to 1 cm².

[0089] Other embodiments are within the following claims. For example,in FIG. 7, each of four reel stands 301-304 is occupied, and one ofcarrier rolls 305-308 is included to carry web from each of therespective rolls.

[0090] Only two shower assemblies 309 and 310 are positioned betweencarrier rolls 301 and 302, and between 302 and 303, respectively. Noshower is necessary or desirable between carrier rolls 303 and 304.Instead, the adhesive load from shower 309 is increased to providesufficient adhesive to bond webs 303 and 304.

[0091] In an alternative embodiment (not shown) three-ply tissue may bemanufactured by omitting the roll on stand 301. Shower assembly 310 isoptional in that configuration.

[0092] A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. Apparatus for producing a multi-ply, adhesivelybonded tissue intermediate product, the apparatus comprising: A. a rearreel stand and a rear carrier roll above the rear stand, forming thebeginning of an upper web path; B. a forward reel stand and a forwardcarrier roll above the forward stand, forming the beginning of a lowerweb path, the upper web path converging with the lower web path at theforward carrier roll; C. an adhesive applicator system for applyingadhesive to the bottom of tissue moving in the upper web path, theadhesive applicator system comprising: i. an array of spray nozzlespositioned at a spray location below and generally transverse to theupper tissue path, and oriented to spray generally upward, toward thebottom surface of the upper tissue, the first location being between therear and the forward carrier rolls; ii. an adhesive conduit connected toprovide a flow of adhesive to the spray nozzles, and iii. a pressurizedgas conduit connected to provide a flow of gas to the spray nozzles toatomize adhesive flow through the spray nozzles, D. a pair of nip rollspositioned downstream from the spray head array and the forward carrierroll, the nip rolls being in both the upper and lower tissue paths, thenip rolls forming a nip for compressing the upper and the lower tissuetogether E. a winder downstream of the nip for winding up bonded tissueproduct, the winder being designed to have a running speed within apredetermined range, the nip being spaced apart from the spray locationat least 230 inches, to permit sprayed adhesive to partially but notcompletely set during travel over that web path distance at speeds inthe predetermined range.
 2. Apparatus for producing a multi-ply,adhesively bonded tissue intermediate product, the apparatus comprising:A. a rear reel stand and a rear carrier roll above the rear stand,forming the beginning of an upper web path; B. a forward reel stand anda forward carrier roll above the forward stand, forming the beginning ofa lower web path, the upper web path converging with the lower web pathat the forward carrier roll; C. an adhesive applicator system forapplying adhesive to the bottom of tissue moving in the upper web path,the adhesive applicator system comprising: i. an array of spray nozzlespositioned at a spray location below and generally transverse to theupper tissue path, and oriented to spray generally upward, toward thebottom surface of the upper tissue, the first location being between therear and the forward carrier rolls; ii. an adhesive conduit connected toprovide a flow of adhesive to the spray nozzles, and iii. a pressurizedgas conduit connected to provide a flow of gas to the spray nozzles toatomize adhesive flow through the spray nozzles, D. a pair of nip rollspositioned downstream from the spray head array and the forward carrierroll, the nip rolls being in both the upper and lower tissue paths, thenip rolls forming a nip for compressing the upper and the lower tissuetogether E. a winder downstream of the nip for winding up bonded tissueproduct, the winder being designed to have a running speed within apredetermined range, and F. a lift mechanism attached to said array ofspray nozzles to move said array between a rest position spaced from theupper web path and a an operative position for delivering adhesive toweb moving in the upper web path.
 3. The apparatus of claim 1 or claim 2further comprising: A. a source of adhesive providing a flow of adhesiveto the adhesive conduit; B. a source of pressurized gas providing a flowof gas to the gas conduit; C. a sensor for sensing the speed of travelof at least one of the tissue webs, the sensor providing a web speedsignal to a signal processor; D. an adhesive flow control system forcontrolling the flow of adhesive to the spray heads responsive to webspeed, the adhesive flow control system including an adhesive flowmonitor and an adhesive flow controller connected the signal processor;the signal processor providing signals to the adhesive flow controllerresponsive to the web speed signal and the flow monitor signal, wherebyspray rate is varied in response to web travel rate.
 4. The apparatus ofclaim 3 further comprising at least one intermediate reel stand andintermediate carrier roll, forming the beginning of an intermediate webpath, the intermediate carrier roll being positioned between the rearand the forward carrier rolls.
 5. The apparatus of claim 4 in which thearray of spray nozzles is a rear array of spray nozzles positioned atleast 230 inches from the nip, and the apparatus further comprises afront array of spray heads positioned at a front sprayer location belowand generally transverse to the intermediate web path, and oriented tospray generally upward, toward the bottom surface of the intermediatetissue.
 6. The apparatus of claim 1 or claim 2 characterized in that thepredetermined speed range is a first predetermined range, and theapparatus is positioned to receive webs from web-forming equipment whichincludes a dryer and a winder operating at a speed within a secondpredetermined range, the first predetermined range being fast enough toprocess the output of the web-forming equipment substantially withoutbacklog or slowing of that equipment.
 7. The apparatus of claim 1 orclaim 2 in which the adhesive flow control system includes circuitry tocontrol the amount of adhesive flow supplied to the nozzlessubstantially proportional to the web travel speed, so as to provide asubstantially constant overall ratio of dry adhesive per unit area ofweb at different web speeds.
 8. The apparatus of claim 7 in which theadhesive flow control system comprises circuitry to establish at leasttwo phases, a running phase and a transition phase, the web speedchanging during the transition phase to or from the running phase thetransition phase being substantially slower than the running phase, andthe amount of liquid adhesive delivered per minute is substantiallyproportional to the web speed during both the running phase and thetransitional phase.
 9. The apparatus of claim 8 in which the signalprocessor controls the pressure or flow of nozzle atomizing air inresponse to web speed change between the running and the transitionphase.
 10. The apparatus of claim 1 or claim 2 comprising multiplenozzles at the first location, the nozzles being positioned in a showerhousing which includes a damper that is movable from a first damperorientation that prevents nozzle spray from reaching the moving web anda second damper orientation in which spray reaches moving web.
 11. Theapparatus of claim I or claim 2 further comprising a nozzle purgerincluding a flush water conduit connected to provide flush water to theadheseive flow conduit and to the nozzle.
 12. The apparatus of 11further in which the nozzle purger further comprises a pressurized gasconduit connected via a purge valve between a source of pressurized gasand the flush water conduit, the purge valve being controlled by acontroller to shut the valve when flush water is flowing to the nozzleand then to introduce said pressurized gas when flush water flow iscomplete, thereby purging liquid from the adhesive conduit and from thenozzle.
 13. The apparatus of claim 12 in which a single source ofpressurized gas provides gas flow both for atomizing the adhesive andfor purging liquid.
 14. The apparatus of 13 further in which thepressurized gas is pressurized air.